Does Sculpting create any new Geometry?
Normally sculpting does not add any vertices or edges, it just moves them around. But when you enable the dynamic topology option in the left toolbar T of your 3d view it adds vertices depending on the given value and your zoom level.

You wrote that you want to create a game character? I recommend that you copy your existing object and add more and more details. Then you can bake the normals and save a lot of memory and rendering time.